In the forthcoming 10-20 years, the three projects we are discussing will be completed or launched. E-ELT is currently under construction and is expected to be completed by 2027https://elt.eso.org/about/timeline/. After a 30-year observation for the Lyman-\(\alpha \)  absorption lines of the distant quasar, it will be about 2060 estimated optimistically. Currently, SKA Phase 1 is under construction and is planned to be completed in 2028https://www.skatelescope.org/. Certainly, SKA Phase 2 is also planned for construction, but in this paper, we do not attempt to make detailed forecasts for SKA2 since its precise configuration is yet to be decided. For the detailed discussions of the redshift drift from SKA2 in cosmology, one can refer to Ref. [1]}. After a 40-year observation of SKA1 for redshift drift, it will be about 2070. The proposal of DECIGO and its scientific pathfinder B-DECIGO have been approved, and B-DICIGO is planned to launch in the 2030s to demonstrate the technologies required for DECIGO [2]}. DECIGO is optimally expected to obtain a 10-year observation of GW standard sirens before E-ELT and SKA1 complete the observations described above. Although our forecasts are far out, the results of this paper present the implications of these observations for cosmology in the future and the limits of constraints on cosmological parameters.
